Technical Field
The present invention relates to a light-emitting element driving circuit system, and in particular, to a light-emitting element driving circuit system which drives a plurality of light-emitting elements.
Background Art
Recently, a light-emitting element driving circuit system is equipped in various electronic devices such as a portable phone. For example, Patent Literature 1 (JP 2008-251886 A) discloses a structure having a drive current supplying circuit which is connected in series with a light-emitting element between a first power supply and a second power supply, and which supplies a drive current to the light-emitting element according to a voltage on a control terminal, and a current determining circuit which determines and outputs a current according to an amount of output light of the light-emitting element. The structure further has a current-to-voltage converter circuit which converts a current determined by the current determining circuit into a voltage and outputs the converted voltage to the control terminal of the drive current supplying circuit when the control signal is in a first state, and which disconnects the output voltage terminal from the control terminal of the drive current supplying circuit when the control signal is in a second state. The structure also has a reset circuit which connects the control terminal of the drive current supplying circuit to the second power supply when the control signal is in the second state.
In some light-emitting element driving circuit systems, a plurality of light-emitting elements are placed in a matrix form, and light is sequentially emitted from each light-emitting element for a predetermined light emission period, so that light is emitted in a circulating manner When the predetermined light emission period is longer than a normally set period, if the light-emitting elements are caused to emit light in a circulating manner with the ON-OFF control of each switching element for light-emitting element connected to each light-emitting element being controlled with a preset ON time, a number of switching operations of each switching element for light-emitting element may become large, resulting in an increase in the current consumption of the light-emitting element driving circuit system.